Enzymatic cleaners combine one or more enzymes with one or more surfactants and other cleaning agents in an effort to clean surfaces and lumens. The enzymes used are typically proteases which degrade proteins by cleaving the amino acid chain so that the post-cleavage fragments can be more easily washed away by the surfactants and water present in the cleaner or in an auxiliary product, typically followed by a rinsing step. Yet, while instrument cleaners containing digestive enzymes (proteases) have proven effective in breaking down organic soils and body fluid, the proteases typically added to surgical instrument cleaners have not been shown to be effective at all in the breakdown of prions, protein like substances causing a variety of wasting diseases, especially under conditions of use recommended for such cleaners. In many instances, cleaners and enzymes that have been potentially discussed for relation to removal and deactivation of prion materials, have been indicated under conditions of use that are environmentally unfriendly or excessively corrosive to the materials being cleaned therewith, require pre-treatment with sterilization, oxidizing agents, peracetic acid or pre-treatment at temperatures above 100° C. prior to treatment with an enzymatic formulation.
Enzymes are catalysts that speed up chemical reactions, and are added to cleaning formulations to speed up the cleaning process. However, enzymes are very specific to the substrates they work on and in the manner in which they work. Proteases break down protein peptide bonds of particular types. Lipases break down fats and/or lipids. Amylases break down carbohydrates and starches. A litany of other enzymes catalyze a host of reactions that are not relevant to the present invention.
A major concern in health care facilities has been the proliferation of hospital acquired infections including surgical site infection when surgical instruments are improperly processed. Europe has been concerned for years about prion diseases Creutzkeldt-Jacob disease in humans (vCJD), and the transmissions of such diseases to humans by consumption of meat from infected animals such as Scrapies in sheep and goats, and bovine spongiform encephalopathy, i.e., mad cow disease. CJD and vCJD has been of a lesser concern in the US and in fact may be under reported. However, Wasting Disease in mule deer and elk has reached epidemic proportions and rapidly proliferated in the United States spreading from animal to animal from contaminated saliva, blood, feces and from vegetation (contaminated primarily due to such agents being deposited on soil absorbed during various plant processes including nitrogen fixation). Health care facilities have used lengthy aggressive parameters to re-process instruments exposed to these prion diseases, or have used incineration, or the costly practice of disposing of single use instruments in connection with many procedures when prion infectivity is suspected.
While the US has had few such cases and has only recently awakened to the risk of prion diseases, that awareness and the need to limit the risk substantially has become more and more visible in recent years.
The Center for Disease Control has stated:
Prion diseases or transmissible spongiform encephalopathies (TSEs) are a family of rare progressive neurodegenerative disorders that affect both humans and animals. They are distinguished by long incubation periods, characteristic spongiform changes associated with neuronal loss, and a failure to induce inflammatory response.
The causative agents of TSEs are believed to be prions. The term “prions” refers to abnormal, pathogenic agents that are transmissible and are able to induce abnormal folding of specific normal cellular proteins called prion proteins that are found most abundantly in the brain. The functions of these normal prion proteins are still not completely understood. The abnormal folding of the prion proteins leads to brain damage and the characteristic signs and symptoms of the disease. Prion diseases are usually rapidly progressive and always fatal.
Prions can be transmitted by ingestion of meat infected with prions, and lead to brain wasting diseases. Of greater concern however, has been the actual and potential for transfer of such infectious agents from patient to patient in hospital settings from blood transfusions and from surgical instruments, especially from dirty surgical instruments (and even from apparently cleaned instruments having residual prion contamination), most especially from those instruments used in brain and neurological procedures, and even from instruments used in eye, spleen, appendix, and tonsil surgeries.
While cleaning is the critical first step in the decontamination of surgical instrumentation, the removal of prions by traditional means, enzymatic solutions such as those with protease enzymes, high level disinfection and sterilization even when preceded by high alkaline detergents has not been shown to effectively destroy or remove prions from medical devices. (Furthermore, use of highly acidic (pH 4 and below) or highly alkaline (pH 11 or above) compositions are detrimental to the instrument surfaces needing to be cleaned and therefore cleaners using such pH extreme formulations are only minimally economically more advantageous than using disposable equipment). Prions are believed to cause not only known diseases such as CJD, vCJD, Scrapies and other wasting diseases, but also may have a direct link to other neurological diseases such as Alzheimer's, dementia, Parkinsons Disease, MS and other neurological diseases.
By simply removing prions and rendering them ineffective by specific enzymes in a surfactant blend that is water soluble, free rinsing, biodegradable and environmentally preferred, the simple act of pre-cleaning, cleaning, and rinsing such devices from soiled instruments and equipment can become a major life saving initiative and curb a potential epidemic. While most surgical devices must be incinerated after exposure to prions or, in some facilities, using single use instruments at a huge expense in such cases, most cases of prion disease and transmission are unknown and under reported. The consequences to public health can be catastrophic and the cost to the public health system enormous when such an event occurs and frightening when under reported.
Multi-enzymatic cleaners for medical instruments preparatory to sterilization of such instruments in existing sterilizers generally do not have enzymes that are suitable for attacking prion materials and therefore rely on the “mechanical action” or sonication of the cleaning process to hopefully remove such prion contaminants. While such action can remove a wide range of contaminant materials and soils, not all surfaces can be effectively cleaned by such mechanical action and even where generally effective results can so be obtained, there is still a significant chance of residual contamination. With respect to prion materials, even minute residual contamination is of concern since prion materials can very rapidly convert normally folded materials into improperly folded analogs in an iterative process so that even such small residual contamination can be highly problematic. In 2005, in an article published at http://www.brown.edu/Administration/News_Bureau/2005-06-05-109.html. entitled “Prions Rapidly “Remodel” Good Protein Into Bad, Brown Study Shows”, it was reported by Serio et al, in an article published in Nature, that prions convert healthy protein into abnormal protein through an ultrafast process similar to DNA replication. Thus, prion contamination has become a growing concern in the medical field. Other compositions require conditions of use to obtain prion disinfection with extreme pHs (generally under pH 4 or over pH 11) making them unsuitable for use with the substrate being cleaned. Other methods require long exposure times from at least one hour to 48 hours to an enzymatic formulation or require multiple steps which may still be ineffective and have the potential to delay surgical procedures and affect patient care.
Similar concerns of contamination with prions have been raised in connection with meat processing plants due to the possibility of an infected animal not presenting with symptoms before slaughter not being detected.